The principal objective in the proposed research will be to investigate how resonant Raman scattering can be used as a probe of the active-site structure of heme proteins in solution. Particular emphasis will be placed on the polarization properties of the Raman spectra and their dependence on tunable laser frequency in the region of the alpha and beta transitions, and on determining how this dispersion reflects the local structure at the heme. Measurements of linearly and circularly polarized scattering will be continued in several low-spin ferrous hemes showing pronounced dispersion: ferrocytochrome c, carboxymethylated cytochrome c, the undecapeptide of cytochrome c, and the cyanide derivative of reduced horseradish peroxidase. The resonance scattering near the alpha band will be studied in detail, using low temperature and a magnetic field to resolve and modify the splitting and mixing of the Qoo states. Identification of vibrational modes and their structure sensitivity will be carried out using normal-mode analysis and samples which have had selective isotopic substitution. Finally exploratory measurements of new and different heme proteins will be continued to look for resonance Raman spectra which give structural insight into catalytic function. Systems studied will include cytochrome P 450, chloroperoxidase and several forms of horseradish peroxidase.